Slender-billed curlew description

Among the world’s most endangered and least understood bird species, the slender-billed curlew (Numensis tenuirostris) is the rarest bird in Europe, North Africa and the Middle East (5)(6). Challenging to identify because of similarities to the Eurasian curlew (Numenius arquata) and the Whimbrel (Numenius phaeopus) in particular (5), this medium-sized wader is a mottled brown-grey colour, with white underparts that are marked with black, often heart-shaped spots on the flanks (7). The sexes are similar in appearance, although the female is generally larger in size (2). It is a small, pale curlew, best identified by its long, slender beak, which is slightly decurved and tapers to a fine, narrow tip. The legs of the slender-billed curlew are dark grey, in contrast to the longer, paler bluish-grey legs of the Eurasian curlew (2)(5). The common name is derived from the soft 'cour-lee' call given in flight (7).

Related species

Slender-billed curlew biology

Very little is known about the natural ecology and behaviour of the slender-billed curlew due to the rarity of this species (5). In 1914, a single nest was found which contained four eggs, and a colony of 14 nests was subsequently reported from the same site (8). The slender-billed curlew feeds by walking slowly and occasionally pecking at the surface until a food item is located, and are reported to prey on earthworms, insects and molluscs(8).

Slender-billed curlew range

The slender-billed curlew is an elusive migratory species, and despite numerous searches throughout its range, there have been no uncontroversial sightings since it disappeared from its last known, regular wintering site at Merja Zerga, Morocco, in February 1995 (8). The only breeding site ever confirmed is near Tara in Siberia, from which nests were recorded between 1914 and 1924.

The slender-billed curlew migrates southwest from Siberia, through several central and eastern European countries such as Ukraine and Hungary, to Mediterranean and North African wintering grounds. There are also a few wintering records from the Middle East (1)(8).

Species with a similar range

Slender-billed curlew habitat

During its migratory passage through Europe, the slender-billed curlew uses a variety of different habitats including saltmarsh, steppe grasslands, fishponds, saltpans and brackish lagoons; wintering grounds show a similarly diverse range (8). It is particularly associated with large wetland complexes and may be found feeding a few kilometres inland from wetland roost sites (5). Due to the paucity of sightings, the breeding site near to Tara, Siberia is assumed to represent typical nesting habitat and consists of taiga marsh at the northern limit of the steppe-forest zone (7).

Species found in a similar habitat

Slender-billed curlew status

The slender-billed curlew is classified as Critically Endangered (CR) on the IUCN Red List (1), and is listed on Appendix I of CITES (3) and Appendix I of the Convention on Migratory Species (CMS or Bonn Convention) (4).

Slender-billed curlew threats

The decline in the population of slender-billed curlews may have been due to the extensive hunting of waders for food in the latter half of the 19thand early 20th Century. Curlews were a prime target due to their large size, and slender-billed curlews may be tamer than other species making them easy targets (8). The threat of hunting remains, and the continued loss and degradation of wetlands in the Mediterranean and North Africa, as well as in the breeding and staging areas, is also a serious threat (7). Population estimates made in 2000 put the number of slender-billed curlew at fewer than 50 individuals (7).

Slender-billed curlew conservation

The slender-billed curlew is protected in the majority of range states through which it passes, and is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES) (7). It is also listed on Appendix I of the Convention on Migratory Species (CMS), under which a Slender-billed Curlew Working Group (SbCWG) has been established, in the framework of a ‘CMS Memorandum of Understanding’ for the species (5)(9). The group works to allow the cooperation of scientists and governments for the conservation of this species (9), and BirdLife International produced an Action Plan for the conservation of this species in 1996 (8).

Since 2008, members of the SbCWG have launched what is billed as ‘the greatest Western Palearctic birding challenge’, a final, coordinated push to find any remaining individuals of the species before it is too late. If the slender-billed curlew is to be saved from extinction, it must first be relocated, and individual birds should be trapped and satellite tagged to determine important sites, so that any threats can be minimised and this enigmatic species can be better understood (5)(8).

Authentication

Glossary

Brackish

Slightly salty water.

Molluscs

A diverse group of invertebrates, mainly marine, that have one or all of the following; a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.

Taiga

The sub-arctic forest of the high northern latitudes that surrounds the pole and is mainly composed of coniferous trees.

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